Fuel burner control



May 29, 1945. s. G. ISSERSTEDT FUEL BURNER CONTROL Filed March 25, 1942 ill CLOSED wneu con. 11

\5 ENERGIZED LATCNED CLOSED UNTIL (ML 55 \5 OENERG\ZEO CLOSED WHEN LOIL 55 I5 ENERGDZED OPENED WHEN (.OIL l'l l5 ENERG LED INVENTOR. V gfma (1. IaacrshElk- Affowzcy- Patented May 29, 1945 UNITED STATES PATENT OFFICE I rnor oi Delaware to Minneapolis-Honeywell Company, Minneapolis, Minn, a

corporation Application March 25, 1942, Serial No. 486,139

(01. lib-28) 18 Claims.

This invention relates generally to automatic control systems for iluid fuel burners and is moreparticularly concerned with that type 0! system which employs a device responsive to the rate of change oi the temperature of combustion tor the purpose oi sensing the appearance or disappearanceoiailsmeattheburner.

In prior art iuel burner control systems which employ a device responsive to combustion, it is usual to employ a device which will assume one position in the presence oi combustion and a second position in the absence oi combustion. This leads generally to the utilisation 01" hot and cold switches wherein the hot switch is closed upon the establishment of combustion and remains closed until combustion ceases at which time the cold switch is closed, and the cold switch will remain closed until combustion is again established. One of the principal 'obiects oi the present inventlon is to design a system using a diiierent type of combustion responsive device; that is, one which responds to the rate oi change oi the temperature of combustion, or radiation produced by combustion and which will thereiore assume a first position when the temperature of combustion is increasing above a predetermined rate. a second position when the temperature of combustion is decreasing at a rate above a predetermined value. A further oblect oi the invention is to bias the combustion responsive device to a mid or intermediate position which it will assume when the rate oi change 01' com l lfll is less than some predetermined rate.

A further object 01 the invention is to provide a control system ior use with a combustion responsive device oi the above type and arrange this system so that upon the establishment of combustion the combustion responsive device will move to a iirst position to render the safety switch inoperative to open the control circuit and then terminate ignition as said combustion responsive device returns to its intermediate pontion. and then prevent operation of the burner motor when the combustion responsive device moves to a sec ond position in response to the disappearance oi ilame oi the burner, and not permit burner operation until said combustion responsive device has returned to its intermediate position.

A further obiect or the invention is to provide a control system of the above time with a pair of relays having interlocked switching mechanism to provide for the proper operation or the safety switch heater and the ignition device. This switchwillbeclosedbytheilrstrelaytobeener. gisedandwill thenbeopenedby theseoond relay to be energised. Another switch will be closed by the second relay to be energized and will then remaincloseduntiltheilrstreiaytobeenergised has been deenergised.

ii still further object of the invention is to provide a ilrst relay with amain operating winding ior energizing the burner motor and ignition device and a bucking winding which may be energised by the combustion responsive device upon a subsequent failure oi combustion to prevent operation of the burner motor for a predetermined time following the disappearance of the i'iame at the burner.

These and other objects will readily become apparenttothosewhoareskilledinthe artasthe iollowing specification is read in the light of the accompanying drawing, in which Figure 1 schematically illush'ates a control systemi'or a fuel burner which incorporates the various features of my invention therein.

l 'lgurefllsatopelevationoi'thetworelays utilised by my control system employing the interlocked switching mechanism,

Figuresisasectiontakenalongtheiinesl-l of Figure 2, and

mgureiisadetaiiviewottheinterlocking mechanism employed in with the two relays.

Referring nrst to Figures 2, 8 and i. the reference numerals it and ii indicate two electromagnetic relays having armatures i8 and is which are biased to their unattracted position y means or the biasing springs is and il. Bolerringtol 'igurehthereierencenumeral "indicatesthebaseoftherelay ii whichoarries aooil l1 and core II. The armature it comprises an insulating member it which carries an iron plate Ii which is, in turn. plvotally mounted upon the base it. The biasing spring II is shown as biasing the armature II for rotatlonin a counterclockwise direction. The corresponding portions ottherelay ilaresimilariniormandtherei have not been shown separately.

The flexible contact blades II and I! are carried by the insulating member 2. cl relay i I. The insulating member II also carries two pairs oi' resilient contact blades indicated at ii and I. which are alternately bridged by the electrically conducting member II which is carried y armature II. Thearrangement is such that when the relay ii is energised the bridging memswitohing mechanism is so arranged that one as bar 8| bridges the two blades II and when the .2 as'mass may the brida member ll blades :1. The relay is lasteslow! insulating portion Mia lined a bracket ll. Bracket 30 is prorrided-llitbapairoiearallwhichpivotallycarry tlileyerltwhichiabiasedi'or rotation in a directionasviewedlnligureli bymsansoithebiasingspringtl. Thebrach'et aiaprosidedwithasecondpairoieanllwhich lllvotally oarrythe latch melnber II. The de t hand portion of the latch member 30 overlies the ontheresiiientbladellislocateddirectlybetweenthetwobladesllandthearmature lils provided with a bridging member for electrically connecting these three contact blades when the relayiaenergized Asecondpairoistationan' contactsarsmounted cntheresilientbladesll andthearmature II carriesasecondbridains member for bridging these two contact blades whentberelayisenergiaed.

Aninslilatlngpinll'isreceivedinthehoie shownindottedlinesatllinl'lgm-esandextends between the resilient contact blade 44 and the pivoted lever ll. With the lever II in the positionsbowninthedrawinathepintllsni tion and the contact blade It is to be engaged by the brldains memwlth the two contact blades ll when II is energised. However, when the is rotated in a clockwise direction, and ver I! is released, its-biasingsprhag it will it in a conmter-clockwise direction as seen .tresultinginadepressionoipintl which are the resilient blade ll, downwardly and out of contact with the electricalbridains member. thereby opening the switch formed thereby.

The complete operation of the two relays and E E El lit gfi E: 1

a whole, is, first the energisaticn oi relay ll, seconrlthe energizstionotrclay ll, third,thedeenergisation oi' the relay ii, and finally the deenergization of the relay it. Originally, both of the relays will be deenergised and the parts will therefore assume the position shown in Figures 2, 3 and 4. The only switch closed at thlstime will be the switch formed by the two contact blades t1 and the bridging member N. The latch member II willbeinthcpositionshowninl 'lgurei inwhich the lever it is locked in its clockwise position at which flme the resilient contact blade it will he in a osition to be encased by the bridaina memberoithearmature ll whentherelay ilisenergmd. 'lhereiore, upon energisation oi. the relay it the resilient blades It and it will be electrically connected as will be the blades I. Rotation or the lever II is prevented by the latch ll. Upon a subsequent energizaticn oi the relay II. the armature II will pull in and unbridge the resilient blades I1 and bridge the blades ll. At the same time, the extension It on the armature II will engage the right hand end of the latch resilient contact blade II into ebsaaement with the contact blade 24. At the same time, the latch member II will be rotated to release the lever it and cause it to be rotated in a counter-clockwise 8 direction by the biasing spring it which will resuit in a depression 0! the pin l1 and a movement of the resilient blade 44 out oi engagement with the bridging member carried by the armature it. It will be noted that this counter-clockwise rotalo tionoi'theleverllwillnowlockthelatchmemher It in the position to which it has been rotated by the armature it. Thus, upon a subsequent deenergization of the relay ii, the armature II will drop out and unbridge the contact blades II and is bridge the contact blades Tl again. The latch member II will remain locked, however, and thereiorc, will maintain the resilient blade I in engagement with the blade 21. When the relay It is eenergised the armature it will drop on n It and unbridge the blades 4! and It and will also hit the and ll of the lever ti and cause'lttoro' tale in a clockwise direction as seen 3. This will release thelatch mcmberlrl will permit the resilient contact blade It to ga upwardly under the influence of its bias and rotate the latch member it back to the nosition showninl'igurei. t It will thus be seen that the interlocked mechanism between thetwo relays II and I] provide so for closure oi the switch formed by the resilient contact blade ll when the relay II is energised and the opening of this switch when the relay ii is energized. It will be noted further that this switch cannot be reclosed until both the relays so ill and ii have been deenergiaed and the relay it again energized. It will be noted further that the switch lormed by the two resilient contact blades 24 and II is closed by energization of the relay II and will remain closed until the relay 40 II is deenergised, although the relay ii is deenergised first.

' In Figure l, the two relays have been shown very diagrammatically but the same reference numerals have been used to designate like parts wherever possible. In this figure. the relay II has been shown as comprising a main energizing coil II and an oppositely wound bucking coil ll. The contact blades 4! and bridging member carried by the armature II have been indicated as a stationary contact 48 and a movable switch arm lib. The two stationary switch blades 48 and associated bridging member have been indicated as a stationary contact 43 and a switch arm Ila. The intermediate resilient switch blade has been indicated at u with m actuating pin 41 and the bridging member has again been indicated as the switch arm its. In connection with the relay II. the two switch blades 21 have been indicated as a single stationary contact 21 60 and the two switch blades II have been indicated as a single stationary contact ll, both being engageable by, switch arm ll which, as shown, is indicated as engaging the stationary contact I! when the relay Ii is .deenergised and the con- "tact a, when the relay is energised. 'me we switch blades 24 and II have been given the same reference numerals, as well as the latch II and the projection ill on the armature II. Inc relay H is shown as comprising an energizing coil II.

msmberllanddepressitcauingittomovethe'" bousingporticnll. 'lhetwoportionsliandlt open circuit are hollowed out to form a chamber which contains some suitable ga which expands upon increase in temperature. In the present instance, this gas is air. but it is obvious that various other types of gases. or possibly even liquids may be used. A suitable absorbing member such as a thin sheet oi metal foil. blackened on its surface so as to more readily absorb heat rays. is mount ed within the gas chamber and has been designated as It. The front portion ll of the housing is preferably made oi some material which will readily pass radiant heat therethrough to be absorbed by the metal roll it to rapidly heat the air within the chamber which is dcslsnated at II. The air chamber DI communicates with a diaphragm chamber II by means or the passage II, the diaphragm ll being shown as clamped between the portions I! and I of the housing. The diaphragm II is therefore responsive to the pressure wi the chamber II at one side. It is connected anactuatlng stem II which extends loosely through the housing It as shown at II. The diaphragm it is therefore responsive on the other side to atmospheric pressure.

The switch housing port ll supports a first resilient contact blade I! an a second resilient contact blade ll, both of which are biased against the walls of the housing as shown and hence, out oi engagement with their respective stationary contacts is and II. The stem II has a switch actuating member ll nxed thereto and located between two resilient blades 12 and II. The two blades therefore, tend to bias the stem it to a mid-position in which both of the blades are in open circuit position. The arrangement is such that this corresponds to a mid-position oi the diaphragm ll, and this diaphragm may. if desired. be iormed oi neoprene or some other resilient material which is itseli' biased to a midposition in which both or the contact blades l2 and It are in open circuit position. The dia phragm GI and the two blades 12 and II will therefore assume the position shown in Figure i, when the pressures across the diaphragm is are substantially equal. The air chamber it communicates with the switch housing 01 by means or a restricted opening II.

The operation of the combustion responsive device II should now be apparent. Assuming that the device is so mounted that the radiant heat oil combustion will pass through the front -m':i or the housin and, strike the heat member ll. it will be clear that upon -establishment oi combustion the radiant heat will be absorbed and raise the temperature of the air in the chamber II. This will increase the pressure in this chamber and cause the dia- II to move upwardly as viewed in Fig. 1. thereby moving the resilient blade it into engagement with the stationary contact II. The increased pressure in the air chamber ll will cause air to gradually bleed through the restricted opening II which will result in this pressure beinggradually reduced again to atmospheric at which time the diaphragm It will return to its mid-position as shown-in Figure 1. and the resilient contact blade llfiirill hence be moved to position. when combustion i terminated metal tell I! and the heat'in the will be rapidly dissipated with the chamber ll result that the at the burner the-heat absorbed by the 3 tact blade I! to move into engagement with the stationary contact ll. Air will gradually through the restricted opening ll into the her II and return this chamber to atmospheric pressure at which time the diaphrsam II will return to its mid-position thereby moving the resilient contact blade I! again to its open circuit position. It willthusbeseen thatupcn thesatablishment of combustion the switch I8, II is closed for a certain period or time depending upon the size oi the restricted opening II and sainuponthecessationotccmbusiionoitheburner the switch II, II is closed for acertain period of time which is also dependent upon the else of the restriction II. Thus, the combustion responsive device ll. responds to the rate or change or the temperature of combustion and this rate may be adjusted by dlustlns the sins of the restriction II.

If desired. the switch housing It may be entirely enclosed and sealed from the atmosphere and the desired results will be obtained by an equalization or the pressures in the air chamber 00 and in the switch housing It through the restricted opening ll. Actually, this is the preferred construction since it prevents dirt from getting at the switch contacts and from getting into the restricted opening II and blocking it.

Actually. this control system may be placed under the control oi any one of a number or various condition responsive devices, but for the purposes oi illustration the condition responsive device has been shown in the form or a room thermostat which comprises a bimetallic member ll which is fixed at one end and which carries at its free end a resilient contact blade II and a second contact blade I! which cooperate respectively with the two stationary contacts I! and II. The arrangement is such that on a decrease in temperature the bimetallic element ll will contract and cause the resilient contact blade to cheese the stationary contact I! at one temperature, and then at a slightly lower temperature the second contact blade .2 will move into engagement with this stationary contact 00.

Any oi the usual forms of thermally actuated sai'ety switches may be used but for the purposes oi illustration, the switch is shown as comprising a pair of resilient contact blades It and 81 which are biased to open circuit position but which are latched in closed position by means oi bimetallic blad ll, which is fixed at its lower end and which engages the resilient blade II at its upper end. The blade ll latches the switch blades II primary winding II at thestep-down transIos-mas Il'isconnactedbymeansoitheconductorsfl Operation In Figure l, the thermostat III has been shown in a satisfied condition in which its switches are in open circuit position and the two relays l and II are therefore deenergized. This means that the burner motor SI and ignition device I are deenergized and therefore. there is no combustion present at the burner. The diaphragm 6| of the combustion responsive device is in its mid-position and its two contact blades II and II are therefore in open circuit position. The movable switch member 2! of the relay H is in engagement with its out contact 21 but the circuit in which this switch is located is open because the switch member lid of the relay ll is in open circuit position.

The temperature at the thermostat 80 will therefore begin to decrease which will first cause the thermostat to move the resilient contact blade ll into engagement with the stationary contact 83. This will not establish a circuit at this time, due to the fact that the switch arm lib of the relay Iii is in open circuit position. The temperature will continue therefore to decrease until the thermostat 80 causes the switch blade 82 to engage the stationary contact II. This will establish a circuit from one side of the secondary winding ll through conductor Ml, electric heater ll for the safety switch blade ll, conductor ill, safety switch blades I! and I1, conductor III, contact 83. switch blades BI and 31, contact ll. conductor liil, main energizing winding ll of the relay ll, conductors ill. I and ill! back to the other side of the secondary winding 18. This causes energization of the relay I! and the movement of the armature I! to its attracted position which causes the switch arm 12b to engage contact ll and switch arm Ila to engage the contacts ll and M. Engagement of the switch arm 12b with contact ll establishes a holding circuit through the thermostat II which passes directly from contact ll. resilient switch blade ll. bimetallic element Ill, conductor Ill, switch arm no, contact ll, and conductor till directly to the energizing winding 55 of the relay III. This circult is independent of the switch blade l2 and contacts as, and therefore, the winding will remain energized until the resilient switch blade II is moved out of engagement with the stationmy contact ll. Movement of the switch arm Ila into engagement with the stationary contact I! energizes the burner motor \II by means of a circuit extending from the line wire Bl, through conductor m. burner motor 0|, conductor ill. switch arm in, contact 43 and conductor ll! back to the other line wire ll. Movement of the switch arm Ho into engagement with the contact. ll energizes the ignition device by means of a circuit extending from the line wire 03 through conductor H8, ignition device ll, conductor Ill, switch arm Il. contact 21, conductor Ill, switch blade .switch arm Ila, conductor I". switch arm "a, contact II and conductor" H2 back to the other line wire II.

It will thus be seen, that upon a call for heat by the thermostat II. the burner motor and ignition device will be simultaneously energized. It will be seen also that the electric heater I! for the safety switch is in the energizing circuit and holding circuit for the energizing winding ll of the relay ll so that if this electric heater re-- mains energized for a predetermined period of time this will cause the blade ll to warp to the left and release the safety switch blade I]. for movement to open circuit position. This will decnergize the relay I0 and therefore. deenergize the burner motor Ii and ignition device If. The system is then effectively locked out until the safety switch is reset by means of the manual reset button ill.

Normally however, combustion will be established which will cause the air in the chamber ii to expand and move the diaphragm it in a direction to cause engagement between the resilient contact blade II and the stationary contact II. This will establish a circuit from one side of the secondary winding I! through conductor I00, safety switch heater ll, conductor liil, safety switch blades II and 81. conductor I02, contact ll, resilient blade Ii, bimetallic element N. conductor I01, switch arm lib, contact 45, conductors Ill and I", resilient contact blade 13, contact 18, conductor III, winding ll of the relay ii, and conductors I22 and I08 back to the other side of the secondary winding II. The eatablishment of thi circuit, therefore. results in the energization of the relay II with a resultant movement of the switch arm 28 out of engagement with contact 21 and into engagement with contact 28. This sets up a new circuit for the ignition device which extends from the line wire I! through conductor I ll, ignition device 8!, conductor ill, switch arm 28, contact 2! and condoctor ill back to the other supply line ll. At the same time, the armature I! of the relay H rotates the latch member ll in a direction to release the lever I! which rotates in a direction to lower the pin II as seen in Fig. 4, or to raise this pin as seen in Figure 1. to move the resilient contact blade it to open circuit position. This resilient contact blade, it will be remembered, was in the original energizing circuit for the ignition device 82.

The extension I on the armature IS in rotating the latch 38, also moves the resilient contact blade II into engagement with the contact blade II. This establishes a shunt circuit around the safety switch heater I! which effectively deenergizes it. This circuit comprises the conductor III, switch blades 24 and ti. and conductor Ill. It will be recalled that the latch 3| in releasing the lever 3! looks itself in the position to which it is moved by the armature ll and therefore. effectively locks the switch blades II and II 111 closed circuit position. These switch blades will remain in closed circuit position until the relay ill is deenergiled to raise the lever 88 and release the latch member ll.

After a predetermined time interval. the pressure across the diaphragm II will be equalized due to the restricted opening ll. thus causing a return of the diaphragm II to its mid-position and a return of the resilient contact blade II to open circuit position. Such action deenerglnes thewinding I! for the relay II and this relay drops out causing the switch arm I! to move out of engagement with contact 28 and into engagement with contact 21. This deenergizes the ignition device because the resilient contact blade II has now been moved to open circuit position. As set forth above, the resilient contact blades II and I! remain in closed circuit position and therefore. the safety switch heater to remain: deenergized. This is the running condition of the system.

One of the advantages of this system may be noted at this point. and that is that the ignis.

ticn device is not desnergiled immediately upon the establishment of combustion, whereas the safety switch heater 80 is deenerg'lsed immediately upon establishment of combustion. More specifically, it is the engagement of the contacts I3 and II which results in the energization of the relay Ii and the deenergization of safety switch heater I0, whereas the ignition evice is not deenergised until the pressures across the diaphragm ill have been equalised through the restriction ll resulting in the opening of the 7 switch". II. This timing can obviously be adiusted by adjusting the size of the restriction 18 or the position of contact II. It will be noted that although the energization'oi the relay ll caused the opening or the switch 44, the deenergisation of this relay will not result in the reclosure of this switch due to the tact that the lever I! remains in its tripped position in which it causes the stem 41 to depress the switch blade I. This blade will remain in open circuit position until the relay II has first been deenerglsed and then reenergised. The system will remain in this condition as long as combustion remains at the burner and as longmthethermostat It continues to call for heat. V a

when the thermostat It becomes satisfied it will move the resilient contact blade ll out of engagement with the stationary contact It and therefore. deenergize the energizing winding II of the relay III. This will result in a deenergization oi the burner motor 8|. Deenergization of the relay ill will also reset the lever 35 upon the latch member 8', thereby permitting the switch 2|, it to move to open circuit position and also permitting the resilient blade'llto move to a position where it will again be engaged by the switch arm lie and the relay i is again energised. The resultant cessation of combustion at the burner will cause the air within the chamber II to contract and lower thepressure therein and the diaphragm OI will therefore move downwardly and cause the resilient contact blade 12 to engage stationary contact H. Although this switch is in circuit with the bucking winding II. this winding will not be enersisedat this time due to the fact that the'circuit silillhe open at the thermostat It. However. tlm circuit at the thermostat Ill be reclosed beiore the pressures have equalised across the diaphragm is, the relay it could not be energised due to the fact that both the energised winding 55 and the bucking winding ll would both be eneraised. The energizing circuit for the winding lil would be the same as traced above in connection with the original energization oi the circuit. The circuit tor the bucking winding It extends from one side ortho secondary winding ll through conductor Ill, safety switch heater ll, conductor Ill, safety switch blades II and 81, conductor "I, contact II, switch blades ii and II, contact ll, conductor ill, conductor Ill, conductor m, resilient switch blade It. contact 14, conductor Ill, bucking winding 86, and conductors Ill, III and iii! back to the other side of the secondary winding II. It will thus be seen that once the burner motor Ii has been d by the thermostat ll, or for that matter due to a momentary power failure, and then the circuit reclosed immediately it will be impossible for the burner motor Ii to be reenerglsed until the pressures across the diaphragm ll have had a chance i to equalize following the change in pressure in theairchamberllcausedbycsssationofcomp bustion at the burner. In other words. the combustion responsive device II with its restriction II provides for the proper recycle timing of the system.

I In the event that the system should be operating normally and a dame failure should occur. the air in the chamber II would immediately contract and reduce the pressure therein, thus causing the resilient blade II to en'glle the contact is. This would result mine energization oithe bucking winding "by manner the circult lust" traced above with the result that the rally jl would drop outand deeiierlile'the burner materiel, The relay is would remain deenergised until the pressures across the diaphragm II have equalised and caused the resilient contact blade 12 to return to open circuit position. During all this time, the energizing winding it would remain energised. The relay It would then pull in and reeneigize the burner motor Ii and ignition device I! and the system would attempt to start normally. If combustion was not established then the sai'ety switch heater ll would cause the safety witch to open andlock the system out until the trouble was corrected and the system manually reset."

As many changes and modifications or this invention will undoubtedly occur'to those who are skilled in the art, I wish it'jto be understood that I intendtobe limited only by the scope of the appended claims and not by .the'speciflc embodiment of the invention which has been disclosed herein merely for the purposes of illustration.

'Iclaimasmyinvention: p

i. A duid iuel burner control system com rising in: combination,.mesns includiijglan electric device incontrol or a burner, a device responsive to the rate of change of the temperaturerof combustion, means includins a relay for energising saidelectri'c device, said relayhavingamainwlndlnsandabuckinswindins. amainswitchclosedinresponsetoademand for burner operation. an circuit for said relay including said main switch and main 45 winding, and a normally open cold switch closed by said combustion responsive device when the temperature of above a Pr determined rate, and by said cold switch for in parallel withsaid main winliingwhereby said relay will be eflectively deenergis'edf r of whether said main switch is open or. closed.

2. A fluid fuel burner control system comprising in combination, means including an elec- M trio device in control of the delivery of fuel to a burner, a device responsive to the rate of change of the temperature of combustion. a normally closed, thermally open safety switch in control of said electric device. shelter tor said safety to switch, means including a con it n device for: electric devioe iand heater upon a demandfor burner operation, means operated by said combustion responsive device for deenergizingssid heater when some heat of combustion above a predetermined rate a open cold switch closed by said combustion responsive device when the temper-shire of combustion above aprodetermined rate. and by said 10 cold switch for preventing of said electricdevicssslong sssaidcoldswitchisclosed.

s. t-iiuid fuel burner control system comprisingin combination; means 7 ihciudinganeleotric devlceincontrolofthedeliveryoffueltoaburn- 7| er.adsviceresponsivetotbsrateof switcnmainwmdins the temperature of combustion, a normally closed, thermally open safety switch in control of said electric device, a heater tor said safety switch, means including a relay for energizin said electric device, said relay having a main winding and a bucking winding. a main switch closed in response to a demand for burner operation, an encircuit for said relay inclu i said main switch. main winding and heater, means operated by said combustion responsive device for deenergisins said heater when the heat of combustion increases above a predetermined rate. and it normally open cold switch closed by said combustion a device when the temperature of combustion decreases above a predetermined rate, means controlled by said cold switch connecting said bucking winding in parallel with said main winding whereby said relay will be en'ectively deenergis regardless or whether said main switch is open or closed.

4. A fluid fuel burner control system comprising in combination, means including an electric device in control of the delivery ofiuel to a burner,adeviceresponsivetotherateotchangeol' the temperature of combustion, a normally closed, thermally open saiety switch in control of said electric device, a heater for said safety switch, means including a relay for energizing said electric device. said relay having a main winding and abuckingwindinmamainswitchclosedlnnepouse to a demand for burner operation, an energlxinl circuit tor said relay including said main and heater, a second relay, a normally open hot switch closed by said combustion responsive device when the temperature of combustion increases above a predetermined rate, means Including said not switch for energizlng said second relay, means operated by said second relay when energised for deenerglzing the heater for said safety switch, and a normally open cold switch closedby' said combustion responsive device when the temperature of combustion decreases above a predetermined rate. means controlled by said cold switch for connecting said bucking winding in parallel with said main windlng whereby said relay will be effectively deenergiaed regardless of whether said main switch is open or closed.

5. A fluid tuel burner control system comprise ing in combination, means including an electric device in control of the delivery or fuel to a burner, a device responsive to the rate of change of the temperature oi combustion. a normally closed, thermally open safety switch in control of said electric device, a heater for said safety switch, means including a relay for energizing said electric device, said relay having a main windin and a bucking winding, a main switch closed in response to a demand for burner operation. an energiaing circuit for said relay including said main and heater, a second relay, a normally open hot switch closed by said combustion responsive device when the temperature or combustion increases above a predetermined rate, means including said hot switch for enersaid second relay, means operawd by said second relay when energised for deenergizins the heater for said safety switch, means controlled by said first relay for maintaining said heater deenerglzed, once it has been deenergiaed by said second relay, until said first relay has been deenergised and the energizing circuit therefor reclosed. and a normally open cold switch closed by said combustion responsive device when the temperature of combustion decreases above a predetermined rate, means controlled by said cold switch for connecting said bucking winding in parallel with said main winding whereby said relay will be effectively deenergized regardless of whether said main switch is open or closed.

6. A fluid fuel burner control system comprising in combination, means including an electric device in control of the delivery of fuel to a burner, a device responsive to the rate of change of the temperature of combustion, a normally closed, thermally open saiety switch in control of said electric device, a. heater for said safety switch, means including a first relay for energizing said electric device, a main switch closed in response to a demand for burner operation, an energizing circuit for said relay including said main switch and heater, 0. second relay, a hot switch closed by said combustion switch while the temperature of combustion is increasing above a predetermined rate, an energizing circuit or said second relay including said hot switch, switch means actuated by said second relay for deenergising said heater. and means controlled by said first relay for maintaining said heater deenergised. once it has been deenergised by said second relay, until said first relay has been deenergised and the energizing circuit therefor reclosed.

'l. A iluid fuel burner control system comprising in combination, means includins an electric device in control of the delivery of fuel to a burner, a device responsive to the rate of change of the temperature of combustion. a normally closed, thermally open saiety switch in control 0! said electric device, a heater for said saiety switch, means including a first relay for energizing said electric device. a main switch closed in res onse to a demand for burner operation. an energizing circuit for said relay including said main switch and heats a second relay, a hot switch closed by said combustion switch while the temperature of combustion is increasing above a predetermined rate, an energlaing circuit for said second relay including said hot switch, a heater switch, means including said heater for eflectively deenergising it, means operated by said second relay, when energised for closing said heater switch and latching it closed, and means operated by said first relay, when deenergised. for tripping said latch to permit said heater switch to move to open position.

8. A fluid fuel burner control system comprising in combination, means including an electric device in control of the delivery of fuel to a burner, means for igniting said fuel, a main switch closed in response to a demand for burner operation, a circuit for simultaneously energising said electric device and igniting means, said circuit including said main switch, meam movable in response to the rate 01 change of the temperature of combustion, said last mentioned means normally occupying a first position, said means moving to a second position while the rate of change is above a predetermined value incident to the establishment of combustion and returning to its first position as said rate oi change approaches zero, and means operated by said combustion responsive means as it return: to its first position for deenerglzing said lgnitin means.

9. A fluid iuel burner control system comprising in combination. means including an elects-a device in-control i the delivery of fuelhtoi burner, means for igniting said fuel, a mail switch closedin response to a demand for burner operation, a first relay for simultaneously energizing said electric device andestablishlng a first circuit to said igniting means for energizing the same, an energizing circuit for said first relay including said main switch, a hot switch, means for closing said hot switch lnresponse to the increase of the temperature of combustion above a predetermined rate incident to the establishment of combustion and opening said hot switch again as said rate of increase approaches zero, a second relay, an energizing circuit therefor including said hot switch, and means operated by said second relay when energized for opening said first circuit to said igniting means and establishing aseeond circuit therefor, means operated by said second relay, upon"de"energization thereof, for opening the secondcircuit to said igniting means to deenergize the same.

A fluid fuel burner control system comprising in combination, means including an electric device in control of the delivery of fuel to a burner, means for igniting said fuel, a main switch closed in response to a demand for burner operation, a first circuit for said igniting means, a first ignition switch in said circuit, an energizing circuit for said first relay including said main switch, said relay when energized causing energization of said electrical device and closure of said first ignition switch to energize said igniting means, a second relay, a hot switch, means for closing said hot switch in response to the increase in the temperature of combustion above a predetermined rate incident to the establishment of combustion and opening said hot switch again as said rate of increase approaches zero, an energizing circuit for said second relay including said hot switch, a second circuit for said igniting means, a second ignition switch in said last named circuit, means operated by said second relay when energized for opening said first ignition switch and closing said second ignition switch to maintain energization of said igniting means, means operated by said second relay, when deenergized,

for opening said second ignition switch, and

means controlled by said first relay to prevent reclosure of said first ignition switch until after said first relay has been deenergized and then energized again.

11. An automatic control system for fluid fuel burners comprising in combination, means including an electric device in control of the flow of fuel to a burner, means for igniting said fuel. a safety switch in control of said electric device and igniting means a thermal actuator for said safety switch, a heater for said thermal actuator, a condition responsive device simultaneously energizing said electric device, igniting means and heater upon a demand for burner operation, means responsive to the rate of change of the temperature of combustion, and means actuated thereby upon an increase in said rate of change indicating the establishment of combustion for deenergizing the heater for said safety switch, means including said last mentioned means operating to deenerglze said igniting means upon a subsequent decrease in said rate of change.

12. A iluld fuel burner control system comprising in combination, means including an electric device in control of the delivery of fuel to a burner, means for igniting said fuel, a main switch closed in response to a demand for burner operation, a thermally actuated safety switch in control of said electric device and igniting means, a heater for said safety switch. a first relay for simultaneously energizing said electric device and igniting means, an energizing circuit for said first relay including said main switch and heater, 3. second relay, a hot switch, means for closing said hot switch in response to an increase in the temperature of combustion above a predetermined rate and opening said hot switch as laid rate again approaches zero, an energizing circuit for said second relay including said hot switch, a heater switch, means including said heater switch effective when said heater switch is closed to establish a shunt circuit around said heater for effectively deenergizing it, means operated by said second relay, when energised, for closing said heater switch and latching it closed, and means operated by said first relay, when deenergized, for tripping said latch to permit said heater switch to move to open position.

13. A fluid fuel burner control system comprising in combination, means including an electrlc device in control of the delivery of fuel to a burner, means for igniting said fuel, a main switch closed in response to a demand for burner operation, a, thermally actuated safety switch in control of said electric device and igniting means, a heater for said safety switch, a first circuit for said igniting means, a first ignition switch in said circuit, an energizing circuit for said first relay including said main switch and heater, said first relay, when energized, simultaneously energizing said electric device and closing said first ignition switch for energizing said igniting means, a second relay, a hot switch, means for closing said hot switch in response to the increase in the temperature of combustion above a predetermined rate incident to the establishment of combustion and opening said hot switch again as said rate of increase approaches zero, an energizing circuit for said second relay including said hot switch, a heater switch, means including said heater switch effective when said heater switch is closed to establish a shunt around said heater for effectively deenergizing it. said second relay, when energized, closing said heater switch and latching it closed, a second ignition switch in a second circuit to said igniting means, means operated by said second relay, when energized, for opening said first ignition switch and closing said second ignition switch to maintain energization of said igniting means, means operated by said second relay, upon deenergization thereof, for opening said second ignition switch to deenerglze said igniting means, and means operated by said first relay, upon deenerglzationthereof for tripping said, heater switch to permit opening thereof.

14. A fluid fuel burner control system comprising in combination, means including an electric device in control of the now of fuel to the burner, hot and cold combustion switches both biased to their open position, means responsive to the direction and rate of change of combustion chamber temperature for closing said but switch while the combustion chamber temperature is rising and for closing said cold switch while the combustion chamber temperature is falling, a first relay in control of said electric device, a main switch for energizing said first relay and hence said electric device in response to a demand for burner operation, means for igniting the fuel delivered to the burner, means operated by said first relay for rendering said igniting means operative, means including timing means for deenergizing said electric device and igniting means after a predetermined period of time. a

second reley. means including said hot switch tion oi Illd burner, aid control epperetue comprilineenelectricdevioe odwtcdtobe connected can menu for ceueing operalotter whenever llld device is enerie loceted and responsive when coexreteoichensecithetemnentureoi' e normally open cold switch closed eeid neponeive device when the ieeubiecbedtoadecreeeeinthetemperaoi comhulflcn ebove e predetermined rote. meme adopted to be connected to acid main lIitch ice cousin: enercintlon oi'eeid electric decioeureoieeidmeinswltch'ondmeem controlled by said cold switch icr preventing enerzization of aid electric device on ion: as cold cold switch is closed.

16. Fluid fuel burner control emrotue ior use with e fluid i'uel burner luvinc means for controllinl the now of fuel thereto and with e main switch which is closed upon e demand ior oper'etlon of sold burner, said control upper-tile compricing on electric device adopted to be connected to acid ilow controllin: means ior causing operationof the letter whenever said device ll enerailed. hot end cold combustion ewitchec both bineed to their open position, means edapted to be expceed to the temperature oi the combustion chember in which sold humor in located and eil'ective when an exposed to clone said hot Iwitch while the combustion chamber temperature in rllinc end to clcee llld cold ewitch while the combustion chamber tempereture ic iellinc. circuit element! connected to cold electric device and adopted to be connected to acid main switch in such a menner that when sold main ewltch ie cloned leld electric device is enerciaed. meene including timinc meme icideenereillnc said electric device et the end oi a predetermined time intervel, meme controlled by acid hot switch for dieablin eeid timinl menu, and means operated by cold cold switch for deenerlilin eeid electric device independently of aid mein ewitch.

SIEGPRIED G. 188W. 

